1. Field of the Invention
The present invention relates to an image-forming apparatus, and more particularly, to a flat type image-forming apparatus using an electron-emitting device.
2. Related Background Art
A flat panel display is conventionally known as an image-forming apparatus utilizing an electron-emitting device, in which an electron source substrate having many cold cathodes therein and an anode substrate having an electrode and a fluorescent substance are oppositely arranged in parallel with each other, and a vacuum exhausting operation is performed.
For example, such an image-forming apparatus using a field emitter is disclosed in I. Brodie, xe2x80x9cAdvanced technology: flat cold-cathode CRTsxe2x80x9d; Information Display, 1/89, 17(1989), U.S. Pat. No. 5,695,378, etc.
Further, for example, an image-forming apparatus using a surface conduction electron-emitting device is disclosed in U.S. Pat. No. 5,066,883, etc.
The flat panel display can be made light in weight and large-sized in screen in comparison with a cathode ray tube (CRT) display unit widely used at present. In addition, the flat panel display using an electron beam can provide an image of higher luminance and higher quality in comparison with other flat panels such as liquid crystal display, a plasma display, an electroluminescent display, etc.
In particular, the surface conduction electron-emitting device is simple in structure and can be easily manufactured. The surface conduction electron-emitting device also has an advantage in that an electron source substrate in which many devices are arranged in a large area, can be manufactured without a complicated manufacturing process using a photolithography technique as in the field emitter.
FIGS. 12 and 13 show one example of the electron source substrate using the surface conduction electron-emitting device disclosed in Japanese Patent Application Laid-open No. 6-342636 of this applicant.
FIG. 12 shows a plan view of one portion of the electron source. Here, reference numerals 6, 7, 81 and 8 respectively designate a lower wiring, an upper wiring, a surface conduction electron-emitting device and an insulating layer. FIG. 13 is a perspective view in which a peripheral portion of the surface conduction electron-emitting device 81 in FIG. 12 is taken out. In FIG. 13, reference numeral 91 designates a substrate and reference numerals 2, 3 designate device electrodes. Further, reference numerals 4 and 95 respectively designate a conductive thin film having an electron emitting region, and the electron emitting region. The device electrodes 2 and 3 are respectively connected to the lower wiring 6 and the upper wiring 7 electrically insulated from each other by the insulating layer 8. Here, a predetermined voltage is sequentially applied to the upper wiring 7 and the lower wiring 6 arranged in a matrix shape as a scanning signal and an information signal, respectively. Thus, a predetermined electron-emitting device located at an intersection point of the matrix can be selectively operated.
The electron source substrate arranged in such a matrix can be manufactured by using a relatively simple photolithography technique, but a printing technique is preferably used when a larger substrate is formed. In particular, with respect to the upper wiring applying the scanning signal thereto, an electric current amount flowing through this wiring is increased as the number of devices connected to one line is increased. Therefore, a voltage drop due to wiring resistance is caused. Accordingly, it is preferable to reduce the resistance as much as possible by forming this wiring by a thick film.
Japanese Patent Application Laid-open Patent No. 8-180797, etc. disclose a manufacturing method for forming wirings and the insulating layer by a screen printing method. Further, for example, with respect to other members, a manufacturing method for forming device electrodes by an offset printing method, etc. is disclosed in Japanese Patent Application Laid-open No. 9-17333, etc. A manufacturing method for forming the conductive thin film by an ink jet method is disclosed in Japanese Patent Application Laid-open No. 9-69334, etc. The electron source substrate of a large area can be easily manufactured by using such printing techniques.
The surface conduction electron-emitting device will be explained next. The surface conduction electron-emitting device utilizes a phenomenon in which an electron is emitted by allowing an electric current to flow through the conductive thin film of a small area formed on the substrate in parallel with the film surface.
This surface conduction electron-emitting device is formed by using an SnO2 thin film [M. I. Elinson, Radio Eng. Electron Phys., 10, 1290 (1965)], an Au thin film [G. Ditmmer, Thin Solid Films, 9, 317 (1972)], an In2O3/SnO2 thin film [M. Hartwell and C. G. Fonsted, IEEE Trans. ED Conf., 519 (1975)], a carbon thin film [Hisashi ARAKI and others: Shinku (Vacuum), p. 22, No. 1, Vol. 26 (1983)], etc. For example, the applicant of this application proposed a surface conduction electron-emitting device using a palladium oxide film, etc. in Japanese Patent Application Laid-open No. 2-56822.
Generally, in manufacturing the surface conduction electron-emitting device, an electron emitting region is normally formed in the conductive thin film by electric current flowing process called xe2x80x9cformingxe2x80x9d or xe2x80x9cenergization formingxe2x80x9d. In the xe2x80x9cformingxe2x80x9d process, a direct current voltage or a very slow rising voltage, e.g., about 1 V/minute is applied to both ends of the conductive thin film and a gap is formed by locally breaking, deforming or deteriorating the conductive thin film. After the xe2x80x9cformingxe2x80x9d process is performed, the voltage is applied to the conductive thin film and an electric current flows through the device so that electrons are emitted from a region near the gap. At this time, the region emitting the electrons is called the xe2x80x9celectron emitting regionxe2x80x9d.
Further, for example, as proposed by the present applicant in Japanese Patent Application Laid-open No. 7-235255, an activating process is performed with respect to the device terminated in the xe2x80x9cformingxe2x80x9d processing so that the electrons can be more preferably emitted. Similar to the xe2x80x9cformingxe2x80x9d process, the activating process can be performed by repeatedly applying a pulse voltage to the device in an atmosphere including a gas of an organic substance. Thus, carbon and/or a carbon compound is deposited onto the device from the organic substance existing in the atmosphere so that a device electric current If and an emission current Ie are greatly increased.
The surface conduction electron-emitting device manufactured through the above processes has an electron emitting characteristic sufficient as an electron source applicable to an image-forming apparatus such as a flat panel display.
According to a first aspect of the present invention, there is provided an image-forming apparatus, characterized in that:
the image-forming apparatus includes an airtight container (vacuum vessel) comprising:
an electron source substrate in which a plurality of electron-emitting devices connected to m pieces of X-directional wirings and n pieces of Y-directional wirings electrically insulated from each other are arranged in matrix; and
a face plate arranged oppositely to the electron source substrate and having a fluorescent film and an anode electrode (conductive film), and that:
the interior of the airtight container (vacuum vessel) has a region in which widths of the X and Y directional wirings arranged on the outer side of an image forming region are wider than those arranged within said image forming region.
According to a second aspect of the present invention, there is provided an image-forming apparatus, characterized in that:
the image-forming apparatus has an airtight container comprising:
an electron source substrate in which plural electron-emitting devices connected to m pieces of X-directional wirings and n pieces of Y-directional wirings electrically insulated from each other are arranged in matrix; and
a face plate arranged oppositely to the electron source substrate and having a fluorescent film and an anode electrode, and that:
an image forming region substantially formed in a rectangular shape is arranged within the airtight container; and
an outer side of the image forming region in proximity to four corners of the image forming region has a region in which widths of the X or Y directional wirings are wide in comparison with the interior of the image forming region.
According to a third aspect of the present invention, there is provided an image-forming apparatus having an image forming region approximately formed in a rectangular shape, comprising:
an electron source substrate in which electron-emitting devices are connected to m pieces of X-directional wirings and n pieces of Y-directional wirings electrically insulated from each other, and are arranged in matrix; and
a face plate spaced oppositely to the electron source substrate approximately at a constant distance and having an anode electrode arranging a fluorescent film therein,
characterized in that conductive members electrically connected to at least one of the wirings are respectively arranged at four outside corners of the image forming region in proximity to the image forming region.
Preferably, the conductive members are electrically connected to at least one of the wirings except for a most proximate wiring.
In addition, in the image-forming apparatus of the present invention, cold cathodes can be preferably used as the electron-emitting devices. Furthermore, surface conduction electron-emitting devices can be preferably used as the electron-emitting devices.
In the image-forming apparatus according to the second aspect of the present invention, the widths of the wirings on the outer side of the image forming region in proximity to the image forming region are wider than those within the image forming region. Accordingly, an exposed area of a substrate surface can be reduced and charging in this region can be restrained to a minimum.
In the image-forming apparatus according to the third aspect of the present invention, the widths of the wirings are widely set at the four outside corners of the image forming region in proximity to the image forming region. Accordingly, an exposed area of a substrate surface can be reduced and charging in this region can be restrained to a minimum.
In the image-forming apparatus according to the first aspect of the present invention, conductive members electrically connected to at least one of the wirings are respectively arranged at the four outside corners of the image forming region in proximity to the image forming region. Accordingly, the exposed area on the substrate surface can be reduced and charging in this region can be restrained to a minimum. Further, the above conductive members are electrically connected to at least one of the above wirings except for a most proximate wiring so that electric potentials of the conductive members can be prescribed when a device closest to the conductive members is operated.